This invention relates to a dynamic multivane electron arc beam collimator and a dynamic multivane electron arc beam collimation system and related apparatus and methods. The invention is useful in connection with electron arc therapy, which is an electron radiation treatment method used to treat cancer. For example, electron arc therapy is used to treat a patient's chest wall following a mastectomy. The practice of electron arc therapy requires an electron source to provide the electron beam (electron radiation) which is used to treat the target area of the patient. A linear accelerator can be the electron source. A purpose of the invention is to improve the uniformity of dose delivered to a large treatment surface during the technique of electron arc therapy. Dosimetric studies (as detailed in the attached publications list) have shown that an improvement in electron arc therapy dose uniformity can be achieved through application of this invention.
A collimator is used in combination with the linear accelerator to define the shape of the electron field of the electron beam. The shape of the electron field is defined by the collimator's electron aperture. The head of the linear accelerator is moved through or along an arc of rotation above the patient as the electron beam is emitted through the head and collimator to the target area (i.e. treatment area) of the patient. Such movement is referred to herein as "linear accelerator rotation." It is desired that the electron dose be uniform across the target area and that electron radiation to patient areas outside of the target area be minimized.
The following publications include information relevant to an understanding of the invention:
1. Leavitt, D. D., Peacock, L. M., Gibbs, F. A., and Stewart, J. R.: "Electron Arc Therapy: Physical Measurement and Treatment Planning Techniques" Int. J. Radiation Oncology Biol. Phys., Vol. 11, pp. 987-999 (May, 1985). PA1 2. McNeely, L. K., Jacobson, G. M., Leavitt, D. D., and Stewart, J. R.: "Electron Arc Therapy: Chest Wall Irradiation of Breast Cancer Patients" Int. J. Radiation Oncology Biol. Phys., Vol. 14, pp. 1287-1294 (June, 1988). PA1 3. Leavitt, D. D. and Stewart, J. R.: "Optimization of Electron Arc Therapy Doses by Dynamic collimator Control" Proceedings of the 9th International Conference on the Use of Computers in Radiation Therapy, pp. 149-152, June 1987. PA1 4. Leavitt, D. D., Stewart, J. R. Moeller, J. H., and Earley, L.: "Optimization of Electron Arc Therapy Doses by Multi-vane Collimator Control" Int. J. Radiation Oncology Biol. Phys., Vol. 16, pp. 489-496 (February, 1989). This paper was presented at the 29th Annual Meeting of the American Society of Therapeutic Radiology and Oncology, Oct. 20, 1987, Boston, Mass. PA1 5. Leavitt, D. D.: "Multileaf Collimation in Electron Arc Therapy". This paper was presented on May 3, 1988 at the Proceedings of the Twelfth Varian User's Meeting. PA1 6. Leavitt, D. D., Stewart, J. R., Moeller, J. H., Lee, W. L., and Takach, Jr. G. A.: "Electron Arc Therapy: Design, Implementation and Evaluation of a Dynamic Multi-vane Collimator System". This paper was presented at the 30th Annual Meeting of the American Society of Therapeutic Radiology and Oncology, Oct. 11, 1988. Accepted for publication in International Journal of Radiation Oncology Bio. Phys. February, 1989.
Copies of the above-identified publications are filed with this patent application and are incorporated by reference into this specification.
Through the innovations of our invention it is possible to design and construct a dynamic multivane electron arc beam collimator that is attachable to the head of a linear accelerator. These innovations contribute to the ease of use of the collimator and reduce the complexity and size of the collimator without reduction of functionality or features. These innovations facilitate collimator installation and eliminate or reduce the need to modify the linear accelerator.